Inspectors for the agency recently traced the smells from residences in Marysville to the composting plant, twice June 6 and twice again June 25, agency spokeswoman Joanne Todd said.

The citations bring the total to 13 in the past five years for Cedar Grove. The plant has received numerous other odor complaints during that time from people living in Marysville and north Everett. The company also has received four written warnings in those five years.

A Cedar Grove official said information from its odor monitors contradicts the clean air agency’s information regarding the June 6 complaints. As of Friday the company hadn’t yet received the violation notices for June 25, company spokeswoman Susan Thoman said in an email.

“Our on-site electronic odor monitoring system indicated that no detectable odors left our property during the time cited by the (notices for June 6),” Thoman wrote. “We plan to share this monitoring information with the agency.”

The notices won’t necessarily result in disciplinary action against the company.

“It’s up to our supervisors to be able to work through that with Cedar Grove,” Todd said. “And they can appeal it.”

These citations were the first for Cedar Grove in 2013, Todd said.

In 2011, the company was fined $169,000 for odor violations going back several years at both its Everett plant and its plant in Maple Valley, King County.

The company appealed those fines to the Puget Sound Growth Management Hearings Board, a state regulatory panel. The fines were upheld but the board knocked $50,000 off in deference to Cedar Grove’s expenditures on measures to curb the odors.

The board said Cedar Grove to that point had spent $6.5 million on odor control at the two locations combined, some of it voluntarily and some as a result of earlier violations.

Cedar Grove collects yard and food waste from hauling companies in much of Snohomish and King counties and grinds it, cures it and sells it for compost in gardens.

In past years, complaints often have spiked early in the summer, corresponding with an increase in volume of waste being brought to the plant at Smith Island.

Cedar Grove officials have said other sources could be causing the odors. The remainder of Cedar Grove’s fine from 2011 — $119,000 — was put toward an odor study last year by the clean air agency.

The study will combine information from 10 electronic odor monitors, called “e-noses,” and recorded impressions from volunteers in an attempt to scientifically determine the source of the offensive stench.

The total cost of the study is $375,000.The city of Seattle and King County, which both have sent yard and food waste to Cedar Grove for composting, are putting up $100,000 and $50,000, respectively. The city of Seattle recently decided to end its arrangement with Cedar Grove effective next spring. The clean air agency is spending $25,000 on the study.

Four monitors are located at Cedar Grove, having been purchased previously by the company. One monitor each also has been placed at the wastewater treatment plants operated by Everett and Lake Stevens; the Cemex plant in north Everett; the clean air agency’s weather station in central Marysville; one at a volunteer’s home in Marysville and another at a home in Everett.